Poland's Communist Party leaders engaged in an open struggle for power at a crucial meeting last night called to consider harshly worded Soviet citicisms of this country's movement toward greater democracy.

A two-day session of the part's Central Committee, Poland's highest decision-making body, which ended early today, appeared unable to bridge a bitter factional split between supporters and opponents of the party secretary, Stanislaw Kania. A determined attack on Kania's moderate leadership was spearheaded by a fellow Politburo member, Tadeusz Grabski, who with Stephan Olszowski is regarded as a leading spokesman for hard-liners in the party.

The debate, one of the most dramatic since the start of the crisis 11 months ago, ended in some confusion with neither side clearly on top, leaving the Politburo -- the Central Committee's executive body -- deadlocked.

The height of the drama came when Kania, in an almost unprecedented move on behalf off the Politburo that followed Grabski's indirect call for his replacement, proposed that the stalemate in the Politburo be resolved by individual votes of confidence on its 11 members.

The motion was rejected by a majority of Central Committee members, following a stormy debate over procedure.

The latest political upheaval was triggered by receipt of a sternly worded letter from the Soviet Communist Party's Central Committee last Friday demanding firmer action against the independent Solidarity trade union. Whatever Moscow's intentions were in sending the letter, its immediate effect has been to provoke a power struggle at the summit of the Polich Communist Party.

With only five weeks to ge before a major congress of the party, at which a new Central Committee will be elected, some hardliners evidently regarded yesterday's meeting as representing a last chance to gain power. It is expected that most politicians identified with conservative views will be swept from office at the congress.

But the debate that has burst to the surface in Poland also revolves around the unspoken issue of how to avoid a Soviet invasion to roll back the changes that have taken place here since the emergence of the independent trade union, Solidarity.

The Kania group in the leadership apparently believes the best chance lies in building up a new national consensus through the implementation of conciliatory policies towards Solidarity, avoiding open conflicts that might provoke outside intervention.

The hard-liners, on the other hand, seem to think that unless the Polish leadership takes a much firmer line, there is danger that the Soviet Union will do it for them.

Grabski, who long has had a reputation for outspokenness, brought the split in the Politburo into the open. He criticized fellow members of the Politburo for failing to develop a coherent strategy for tackling the crisis, for agreeing to ever-new concessions to Solidarity and for failing to observe Marxist-Leninist doctrine defining the leading role of the Communist Party. m

Then in a direct attack on Kania, who was elected first secretary of the party last September, Grabski said: "In its present composition, under the leadership of Stainslaw Kania, the party is unable to lead the country out of the crisis."

He also charged that several important decisions, including the registration of an independent trade union for farmers, had been taken without the advance knowledge of the Politburo.

Grabski in turn was attacked by Kazimierz Barcikowski, a Politburo member regarded as one of the leading reformers on the Central Committee. Barcikowski spoke in support of Kania's "line of agreement," which he described as "a line of struggle for the security of socialist Poland."

Barcikowski offered to resign, and expressed surprise at Grabski's claim of being kept in the dark.

In a series of fast-moving developments, the Central Committee then adjourned to allow Kania to prepare a reply to Grabski's attack. The party leader used the recess to lobby support from the 49 provincial party chiefs and, according to some Polish sources, from leading Army generals.

Kania is believed to have strong backing from the prime minister, Gen. Wojciech Jaruzelski, who is also minister of defense. Together they have shaped the policy of solving conflicts by negotiation rather than by force.

Following a Politburo meeting during the recess, Kamia proposed that the 140-member Central Committee vote separately on each member of the Politburo. Any Politburo member failing to receive 50 percent approval wold be asked to resign his office.

The Central Committee's decision not to hold such a vote confused political analysts here. It means that for now the present intact -- as has the stalemate between Kania and his opponents. It appears to represent a victory for neither camp, but rather an attempt to preserve a facade of party unity.

The Central Committee debate was held behind closed doors at party headquarters in Warsaw, a huge square building known to Poles as "the White House" because of the original color of its graying facade. The Polish news agency PAP, as well as radio and television, carried fairly detailed accounts of what took place.

Before last summer it was virtually unheard of for such a spectacle of disunity at the top to be aired in public in a communist country. But one result of the reform movement in Poland has been the release of much more official information, including detailed accounts of Central Committee debates.

A complete text of the Kremlin letter, signed by Soviet President Leonid Brezhnev, also was read on Polish television this evening for the first time.

Solidarity's leaders watched the political drama from the sidelines. Ironically, the crisis has coincided with a period of relative labor peace, reflected in yesterday's decision to suspend a strike threat today in four northern provinces.

The strike originally was called to protest the government's failure to name the officials responsible for incidents in the town of Bydgoszcz last March, when Solidarity activists were beaten by police. A parliamentary commission has promised to investigate the matter.

Solidarity's position on the political power struggle is that it is the party's internal affair. Union leaders argue that whoever gains power in the party will need to take into account the wishes and expectations of Solidarity's 10 million members, and that there can be no reversals of reforms already introduced.

In practice, however, the union is bound to be affected by any change in political direction. The adoption of a tougher policy, along the lines advocated by Moscow and the Polish hardliners, almost certainly would result in widespread industrial unrest.

Meanwhile, reform-minded intellectuals yesterday warned of what they called "the disastrous effects" of any Soviet invasion.

The discussion group, called Experience and the Future, said that any attempt to resolve the crisis by outside force would split the party and lead to complete disruption of the economy and the formation of an underground guerrilla movement. International repercussions would include the collapse of the world communist movement, isolation of the Soviet Union, the end of detente and acceleration of the arms race, the statement said.

Before the outbreak of labor unrest in Poland last summer, the group issued a series of proposals for economic reforms, but most were ignored.